@type locale_entry() :: %{
  language: String.t(),
  region: String.t(),
  territory: String.t(),
  locale: String.t()
}

@type locale_key() :: :region | :language | :territory | :locale

@type locale_result() :: %{required(locale_key()) => String.t() | nil}

@type source() ::
  :accept_language
  | :body
  | :cookie
  | :host
  | :path
  | :query
  | :attrs
  | :session